Distribution and morphology of the renin-containing cells in the amphibian kidneys.

Abstract

Studies on the components of the juxtaglomerular apparatus (JGA), the ultrastructural characteristics of juxtaglomerular (JG) cells and the distribution of renin-containing (RC) cells in three species of amphibians were performed in the kidneys by histological, immunohistochemical and electron microscopical methods. The JGA consisted of afferent and efferent glomerular arterioles and JG cells, and there was no extraglomerular mesangium. The macula densa-like structures were observed only in Rana species. RC cells were localized scarcely in a wide range in the walls of afferent vessels, but were not detected in the walls of efferent vessels. In Xenopus species, RC cells were demonstrated numerously in the intraglomerular region. Ultrastructurally, the secretory granules occasionally showed fusiformic structures (containing conglomerated granules). A large number of non-myelinated nerve fibers containing numerous small vesicles and some large dense cored vesicles were observed in the tunica adventitia, and they invaded partly into the concave regions of JG cells. These results suggests that the amphibian JGA is phylogenetically located in an intermediate position between that of fishes and mammals.